1. Technical Field
This invention relates to the field of communications, and more particularly to a method and an apparatus for discriminating speech from voice-band data in a communication network.
2. Description of Related Art
It is well known that the ability to discriminate between speech and voice-band data (VBD) signals, e.g., originating from a modem or facsimile machine, in a communication network can improve network efficiency and/or ensure Quality of Service requirements. For example, although channels of a conventional telephone network each carry 64 kbps, regardless of whether the channel is carrying speech or VBD, speech can be substantially compressed, e.g., to 8 kbps or 5.3 kbps, at an interface between the telephone network channel and a high-bandwidth integrated service communication system, such as at an ATM (Asynchronous Transfer Mode) trunking device or an IP-(Internet Protocol) telephone network gateway. Therefore, because the type of traffic received at such an interface device can dictate the signal processing performed, several techniques for discriminating between speech and VBD signals have previously been proposed. Such techniques conventionally rely on parameters such as zero-point crossing rates, signal extremas, high/low frequency power rates, and/or power variations between sequential signal segments to discriminate speech from VBD.
Although conventional techniques for discriminating between speech and VBD signals generally achieve low error rates for relatively low-speed VBD, the error rate for such techniques increases significantly for discrimination between speech and high-speed VBD transmissions, such as from V.32, V.32bis, V.34, and V.90 modems which utilize higher symbol rates and complex coding/modulation techniques and generate signals with many characteristics which are different than low-speed transmissions. For high-speed VBD, higher error rates occur because the distribution of many parameter values, such as zero-point crossing rates, signal extremas, and power variations, tend to overlap with corresponding speech parameter values.